I just upgraded the calibre windows build to use the newly released Qt 4.7. This should hopefully mean various speedups, particularly in the ebook viewer, as well as basic support for touchscreens (though this is impossible for me to test, since I dont have any touchscreen devices capable of running calibre).
In my testing I've seen startup times fall from between 0-30% (depending on the test system).
However, as with any major upgrade, I'm sure some things broke. I've been using a Qt 4.7 based version of calibre on linux for a few days and nothing that I do seems broken, but I'm sure all of you do a lot of things I don't. I'd appreciate it if we could find those breakages before the next release, so please test
The Qt 4.7 based build is available here:
Note that if you have already upgraded to calibre 0.7.27, you will need to uninstall before installing this build (don't worry, uninstalling will not touch your books or settings).
EDIT: I should add that this build should be perfectly safe (all that's changed is Qt, the toolkit used to draw the calibre user interface, the only bugs I am anticipating are related to calibre not starting/behaving oddly with some input devices/monitors, that sort of thing). If you do experience any such problems, just report them and go back to the normal calibre build.